Summary of work: Personality can be defined in terms of enduring individual differences in emotional, interpersonal, experiential, and motivational styles. The five factors of Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness provide a comprehensive taxonomy of personality traits for the description of personality in aging men and women. Collaborative studies of Canadian and German samples conducted this year confirmed that the five factors and the specific facets that define them are substantially heritable. Anonymous genetic assays of BLSA participants were used in an attempt to replicate claims that the D4DR receptor gene is associated with Novelty Seeking and with aspects of Extraversion. Two extreme groups (Ns = 100) were formed on the basis of personality data; assays found no difference in the frequency of D4DR alleles in the two groups. Studies of the molecular genetic basis of personality will continue.